The present invention relates to a multibeam antenna capable of communicating with a plurality of satellites which are positioned on stationary orbits at the same time.
A prior art multibeam antenna is constituted by a plurality of primary radiators and a single parabolic reflector for reflecting an electromagnetic wave radiating from each primary radiator in a different direction. The primary radiators are located in the vicinity of the focus of the parabolic reflector, or paraboloid, at a suitable distance from each other. A feeder section and a low-noise amplifier are associated with each of the primary radiators in such a manner as to extend along the axis of the antenna.
In the above-described prior art antenna, the deviation of the beams radiating from the parabolic reflector cannot be increased without increasing the distance between the primary radiators. However, an increase in the distance between the nearby primary radiators necessarily results in the shift of the primary radiators away from the focus of the parabolic reflector, whereby the wavefront in the aperture plane of the parabolic reflector is disturbed to lower antenna gain. Another problem with the prior art antenna is that the feeder section and amplifier section directly connected to each of the primary reflectors increase the length of antenna axis because they are arranged along the antenna axis.
For details of such a prior art multibeam antenna, a reference may be made to U.S. Pat. No. 3,852,763 by way of example.